The present invention relates generally to a system for monitoring tire pressures in an automotive vehicle, and more particularly, to a calibration method and system for calibrating the tire pressure system upon assembly and upon the maintenance of the tires.
Various types of pressure sensing systems for monitoring the pressure within the tires of an automotive vehicle have been proposed. Such systems generate a pressure signal using an electromagnetic (EM) signal which is transmitted to a receiver. The pressure signal corresponds to the pressure within the tire. When the tire pressure drops below a predetermined pressure, an indicator is used to signal the vehicle operator of the low pressure.
Various tire manufacturers have suggested various locations for the pressure sensors. Known systems include coupling a pressure sensor to the valve stem of the tire. Other known systems and proposed systems locate the pressure sensors in various locations within the tire wall or tread. Tires are mounted to wheels that are commonly made from steel or aluminum.
During assembly and during routine maintenance such as tire rotation or tire replacement, the tire pressure system must be calibrated. Calibration involves associating the various tire positions with the pressure transmitters that are located on the tires. One proposed method for calibrating a system uses a magnet device to initiate the calibration. Such a device is described in PCT Publication WO 94/20317. In this system, an internal display panel with locations corresponding to the tire location is activated. When the tire locations are illuminated on the display, the vehicle operator or service technician places the magnet near the indicated tire. The transducer then sends a code corresponding thereto to the central controller. When the indicator indicates another tire location, the magnet must be brought near each tire location until each of the tire locations have a tire registered thereto. One problem with this device is that a separate component such as a magnet must be provided to the vehicle operator that is used only in the calibration process. One problem associated with a separate magnet device is that such a device is subject to loss. Thus, the tire pressure sensing system would be rendered inoperable.
Another drawback with such a system is that because many wheels are made from steel and steel is a magnetic material, the various proposed tire pressure sensing systems may not operate properly because the steel wheels may shield the magnetic energy therefrom. Therefore, the system may also be rendered inoperable because the pressure transmitter will not be activated by the magnet.
It would therefore be desirable to provide a tire pressure calibration system that overcomes the drawbacks mentioned above.
The present invention provides a system and method for calibrating a tire pressure monitoring system using an EM transmitter. The present invention includes a first pressure sensor coupled to a wheel of an automotive vehicle. An EM pressure transmitter is coupled to the pressure sensor. The transmitter has a serial number associated therewith. An EM calibration device has a transmitting range. The EM transmitting device has an actuator. When said actuator is activated, a calibration signal is transmitted within the transmitting range. The calibration signal causes the EM pressure transmitter to transmit a serial number. A controller is EM coupled to the pressure transmitter. The controller receives the serial number and associates the serial number with a tire location of the vehicle.
In a further aspect of the invention, a method for calibrating a tire pressure system comprises: generating an EM calibration signal from a transmitter;transmitting calibration information from a tire pressure sensor in response to said EM calibration signal; and receiving said calibration information in a controller.
One advantage of the invention is that the calibration device is preferably incorporated into a remote keyless entry device such as those that are commonly used in automotive vehicles. These devices typically transmit EM signals and therefore can be modified to transmit an additional EM signal to provide the activation signal to the pressure transmitters. This eliminates the problem in the prior art with the expense of a separate calibration tool along with the drawbacks of loss or theft of a separate evaluation tool. That is, because keyless entry devices are coupled to the key chain, they are not subject to easy loss.
Other advantages and features of the present invention will become apparent when viewed in light of the detailed description of the preferred embodiment when taken in conjunction with the attached drawings and appended claims.